In recent years, health hazards and industrial accidents caused by mental fatigue due to overwork have become a social problem.
A flicker test is a known method of measuring mental fatigue. The test relies on human inability to perceive a light pulses, i.e., a flicker, when the light source is flashing at high speeds; however, as the speed (frequency) decreases, perception becomes possible when the frequency is dropped to a certain value. The frequency at which the human perceives the flicker is called a flicker perception threshold, which is known to vary depending on mental fatigue. More specifically, the flicker perception threshold decreases as fatigue becomes more intense; that is, a person cannot perceive a flicker at high frequency when mental fatigue is intense, and perception finally becomes possible when the frequency is dropped to a smaller value than that of a frequency of a flicker that is perceivable by a person in a healthy condition. Using this phenomenon, various flicker test methods and systems were suggested.
For example, Patent Document 1 discloses a system in which a host computer remotely controls a computer terminal in front of the test subject via a network, so as to present some kind of stimulation to the test subject, control the stimulation, and record the reaction of the test subject, thereby measuring the functioning eyesight (actual eyesight) of eyes of the test subject under stress. The document also discloses a method of measurement of flicker perception eyesight to determine the ability to perceive a flicker, as an example of eyesight measurement.
Patent Document 2 discloses a system for reducing the amount of labor necessary for managing the degree of fatigue. The system carries out the presentation and control of flicker stimulation and the measurement of a flicker perception reaction under the control of a computer using a dedicated eyesight-checker containing a light-emitting unit (LED). The degree of fatigue is determined based on the data stored in the computer.
Patent Document 3 discloses a system comprising a flashing light emitting display device and a computer terminal. The flashing light emitting display device presents flicker stimulation under the control of a computer terminal via a communication cable, and the computer terminal records push-button operations as a flicker perception reaction. The measurement data is compared with other data previously stored to estimate the degree of fatigue.